Bulk concatenation of cell array contents (without looping)?

Question

Alex 2011-4-23

3
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https://ww2.mathworks.cn/matlabcentral/answers/6064-bulk-concatenation-of-cell-array-contents-without-looping

编辑： theblueeyeswhitedragon 2018-6-27

Hi,

I have a 1x4 cell whose elements are all 1x40 cells. Each of the elements of the 1x40 cells is a 1000x128 array of doubles.

Is there a way to concatenate the contents of the elements in the 1x40 cells into a 40000x128 array of doubles without looping through the elements individually?

Thanks, Alex

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Answer 1

Matt Fig 2011-4-23

0
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There may be a way to do it with no loops, but I think this is fast anyway. Here is a full example. Just change the numbers according to your needs....

% Make a nested cell array, as you describe it. 
for ii = 1:4  % A 1-by-4 cell
    for jj = 1:3  % Each element is a 1-by-3 cell.
       BC{ii}{jj} = rand(2,5);  %#ok  And each has is a 2-by-5 double 
    end
end
%
%
%
%
% Now extract it.
A = zeros(2*3,5,4);
for ii = 1:4
    A(:,:,ii) = cat(1,BC{ii}{:});
end
A = reshape(permute(A,[1,3,2]),2*3*4,5);